The present invention relates to a system for biodetection applications comprising two basic elements, a substrate with a functionalized surface and a nanoparticle, the system being capable of enhancing the plasmonic effect of the nanoparticle. The invention also relates to a biosensor incorporating such system, in addition to the method for detecting and quantifying a target analyte selected in a sample using such system. Finally, the invention relates to a device which can detect the enhanced optoplasmonic effect of the nanoparticles by means of the system of the invention or by combining the detection of such optoplasmonic effect with the analysis of the changes in the mechanical characteristics in the substrate.